The present invention relates to a steering system for an automotive vehicle, and more particularly to a power-assisted rear wheel steering mechanism adapted for use in a four-wheel steering system capable of steering a pair of dirigible rear road wheels in response to steering operation of a pair of dirigible front road wheels.
Such a four-wheel steering system as described above includes, in general, a front wheel steering mechanism operable in response to a steering effort applied thereto for steering a pair of dirigible front road wheels, a rear wheel steering mechanism including an axially displaceable operation rod operatively connected at the opposite ends thereof with a pair of dirigible rear road wheels for steering the rear road wheels, and a connecting mechanism assembled in combination with the rear wheel steering mechanism and being drivingly connected to the front wheel steering mechanism for effecting axial displacement of the operation rod in response to operation of the front wheel steering mechanism and for controlling the steering angle ratio and direction of the rear road wheels relative to the front road wheels. In the case that a hydraulic power cylinder is assembled within the rear wheel steering mechanism to assist axial displacement of the operation rod, it is required to provide a control valve for the power cylinder in such a manner that the power cylinder is operated under control of the control valve in accordance with the mode of operation of the connecting mechanism.